Heretofore motor vehicle braking systems typically employed mechanical switches which were fastened to the structure of the vehicle as to be in operative contact with the brake pedal for indicating the depression of the brake pedal. Whenever the brake pedal was depressed, the switch closed thereby causing the vehicular stop lights to be energized.
Other prior art systems employed fluid pressure switches which, generally, were connected to the vehicular brake system hydraulic actuating circuitry and were responsive to and actuated by pressure changes in the hydraulic fluid. Such fluid pressure switches, when actuated by a sufficient hydraulic pressure, also served to cause the vehicular stop lights to be energized. Occasionally, fluid leakage would occur, in the area where such pressure switch was mounted, resulting in loss of hydraulic brake actuating fluid and consequent failure of the vehicular braking system.
Still other prior art systems employed in-line mechanical switches comprising an operative connection in the mechanical linkage of the vehicular brake system. Generally, such switches were mounted for movement with the linkage and as such increased the magnitude of the required actuating pressure a force to be applied by the vehicular operator.
Such prior art systems either require a form of adjustment, both when initially assembling the switch into the system and during the life of the system because of linkage wear, or in effect provide an additional weak link in the vehicular braking system. This, of course, involves both labor and additional supporting structure which, when multiplied by the number of motor vehicles built in a given period of time, results in extra costs and expenses.
Further, in such prior art systems, the slight force or pressure applied to a vehicular brake pedal by the vehicular driver, as through the inadvertent resting of the driver's foot on the brake pedal, usually causes the associated switch to be actuated even though the brake system is not being energized. Obviously, having the vehicular stop lights thusly become energized, when the vehicle in fact is not undergoing braking, gives a false warning to the following vehicles thereby destroying the safety value of the stop lights. Also, such prior art switches are generally slow acting and switch failure due to electrical contact erosion is not uncommon.
Automotive vehicles are also often provided with one or more signalling or control devices that ideally provide appropriate signals when the vehicular brakes are actuated. For example, some vehicles are provided with vehicular speed control units which, for safety reasons, should be deactivated as upon initiation of the vehicular braking system. Other vehicles are provided with automatic power transmissions which include means associated therewith for causing the transmission torque converter to lock-up into an operatively solid condition once the vehicle has attained a preselected vehicular speed. Again, for safety reasons, it is desired that the lock-up condition of the torque converter be deactivated upon a preselected vehicular braking force being applied. Further, some vehicles equipped with automatic power transmission assemblies may be provided with interlock means for preventing unintentional vehicle acceleration. This often takes the form of an interlock mechanism preventing the movement of the transmission selector lever from either "park" or "neutral" positions to any other operating condition unless first the vehicular braking system is sufficiently energized. Still other vehicles may be provided with anti-dive type systems or devices which are intended to prevent the excessive downward movement of the front of the vehicle upon energization of the vehicular brake system. Still further, other vehicles may be provided with anti-skid devices, in combination with the vehicular wheel brake assemblies which are sensitive as to the lock-up of the related wheel and which in turn create, at that wheel, a pumping-like action to prevent continued wheel lock-up and instead bring the vehicle to a stop by rapid intermittent energization of the vehicular brake system even though the driver may maintain a maximum force against the vehicular brake pedal assembly. In such anti-skid systems, there are times at which the anti-skid portion of the wheel brake system is desired to be overriden or released from operation.
In any and all of such situations various switches have been employed and calibrated for, in effect, single function duty. Such a proliferation of switches is not only costly but renders each as being a possible source of problems due to, for example, loss of proper calibration or other forms of failure or loss of assured integrity.
The invention as herein disclosed and described is primarily directed to the solution of the aforestated as well as other related and attendant problems of the prior art.